Navy officials say they are not sure if two fighter jets collided before they crashed into the Atlantic Ocean off the North Carolina coast.

Naval Air Force Atlantic spokeswoman Lt. Cmdr. Tiffani Walker said the two Boeing F/A-18 Super Hornet jet fighters were involved in an “in-flight mishap” Thursday morning. She said she could not provide further details, but that an investigation is underway.

The Coast Guard had initially said the jets collided in air before crashing. The jets crashed during a training mission off Cape Hatteras, N.C.